Applicants claim, under 35 U.S.C. xc2xa7119, the benefit of priority of the filing date of Nov. 27, 1998 of a German patent application, copy attached, Ser. No. 198 54 733.1, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optoelectronic component, in particular a scanning unit of a position measuring device for linear and angular measurements.
2. Description of the Related Art
Such a component has been described in the journal F and M, issue 10, 1996, pages 752 to 756. A light-emitting diode is arranged on a photodiode array chip which, by flip-chip technology, or chip-on-glass technology, is connected via gold bumps with strip conductors on a transparent glass plate. The glass plate is also the support of the scanning grating. The space between the photodiode array chip and the glass plate is filled with a transparent underfiller, which contributes to the mechanical stabilization of the structure.
During position measuring by this component, the light of the light-emitting diode radiates through the scanning grating, falls on a scale and is reflected by the scale grating. The reflected light again passes through the scanning grating and falls on the photodiode array, where sinusoidal scanning signals are generated, which are phase-shifted with respect to each other. However, it is disadvantageous in this construction that the underfiller is a very good light conductor, which conducts a large portion of the light radiated by the light-emitting diode directly to the photodiodes of the photodiode array. A high direct light radiation from the light-emitting diode to the photodiodes occurs from the edge radiation of the light-emitting diode and scattered light, generated by scattering in the underfiller. This direct radiation considerably increases the light level of the scanning signals and leads to a detrimental ratio between useful signal and interference signal.
An optical component is known from DE 197 20 300 A1, wherein a light-emitting diode is implanted in a photodiode array.
An object of the present invention is based on disclosing an optoelectronic component, in particular a scanning unit for a position measuring device, which is compactly constructed and wherein the ratio of useful light to interfering light, and therefore the ratio of useful signal to interference signal, is improved.
This object is attained by an optoelectronic component that includes a substrate having a first optoelectronic component, a second optoelectronic component arranged next to the first optoelectronic component and a contact point. A support of the substrate includes a second contact point, wherein the second contact point is located opposite to the first contact point and is in electrical connection with the first contact point. An underfiller in a space between the substrate and the support, the underfiller forms a border area between the substrate and the support toward a space free of underfiller, wherein the border area restricts the space free of underfiller of at least one of the first and second optoelectronic components.
The advantages and objects achieved by the present invention reside in particular in that it is possible in a simple way to keep the space around the light source free of underfiller, and wherein a border area is created by the underfiller, which does not permit the light radiated by the light source to reach the light receivers directly, but instead absorbs or reflects the light. The ratio of the light components of useful light and interference light reaching the light receivers is improved. The level of equality of the scanning signals is reduced and the ratio of useful signal to interference signal is therefore improved.
Exemplary embodiments of the present invention will be explained in greater detail by the drawings.